Potentials. Electron Affinity

MS Monoenergetic electron impact on PH2 (from benzylphosphane) was used, and the ionization efficiency curve was extrapolated to zero ion current. The sharp onset pointed to the adiabatic character of Ej. A measurement with conventional electron energy spread and the usual semilogarithmic method due to [6] yielded Ej = 9.96 eV [2]. 

PES A preliminary He I spectrum of PH2 from the PH3 + F reaction showed a sharp band at the position tabulated above and a broad band in the region 11.0 to 11.5 eV, which was assigned to ionization to PHJ(a B ) [3]. According to [5], however, energetically lower vibrational members of that latter band were probably not seen in the PE spectrum [3], because they were masked by ionization bands from P, P2, and PH3. 

Purely theoretical data with an accuracy of 0.1 eV have been calculated more recently. Ab initio MO theory corrected by 4th order Moller-Plesset (MP4) perturbation calculations [9], gave Ej = 9.72 and 10.64 (for X and a of PHJ) [1, 10]. A modification of that method (to give also singlet-triplet separations) yielded Ej = 9.77 and 10.64 [11]. A treatment of the electron correlation not only by MP4 but also by quadratic configuration interaction (Cl) [12,13] led to Ej = 9.71 [14]. Older data were obtained by Cl [15,16] and SCF [16,17] calculations. - For orbital energies from SCF calculations, see [17, 18]. 

The electron affinities listed in the table below agree within the error limits given. They were obtained by laser photoelectron spectroscopy (LPES) on the PHg ion [19] and PH2 photodetachment using a tunable laser (LPD) [20, 21] or an Xe arc lamp (with a grating monochromator) [21] and ion cyclotron resonance (ICR) spectrometry [20, 21]. All values are reported in two reviews on electron affinities [22] and electron photodetachment [23], and may be considered as adiabatic (see the remarks below the table)  

Electron propagator theory (EPT) yielded a vertical value of 1.160 eV [28] (see also [29 to 31 ]), MP2 theory gave 1.162 eV (zero point correction included) [32], MP4 theory (using isogyric comparisons with the H2 molecule) 1.23 eV [33], and MP4 + quadratic Cl calculations 1.20 eV [14]. Compare also a 1985-review on theoretical calculations of A [34]. HF calculations on PH2 yielded Koopmans Theorem (KT) electron detachment energies, which depend strongly on the basis sets used [35]. Older ab initio MO-SCF calculations gave unsatisfactory results [17]. 

---

The spherical shell model can only account for tire major shell closings. For open shell clusters, ellipsoidal distortions occur [47], leading to subshell closings which account for the fine stmctures in figure C1.1.2(a ). The electron shell model is one of tire most successful models emerging from cluster physics. The electron shell effects are observed in many physical properties of tire simple metal clusters, including tlieir ionization potentials, electron affinities, polarizabilities and collective excitations [34]. 

Quantum chemical descriptors such as atomic charges, HOMO and LUMO energies, HOMO and LUMO orbital energy differences, atom-atom polarizabilities, super-delocalizabilities, molecular polarizabilities, dipole moments, and energies sucb as the beat of formation, ionization potential, electron affinity, and energy of protonation are applicable in QSAR/QSPR studies. A review is given by Karelson et al. [45]. 

HOMO and LUMO energies FMO reactivity indices Refractivity Total energy Ionization potential Electron affinity Energy of protonation Orbital populations Frontier orbital densities Superdelocalizabilities... 

Brus, L. E. (1983). A simple model for ionization potential, electron affinity and aqueous redox potentials of small semiconductor crystallites. /. Chem. Phys., 79, 5566-5571. 

Bms LE (1983) A simple model for the ionization potential, electron affinity, and aqueous redox potentials of smaU semiconductor crystaUites. J Chem Phys 79 5566-5571... 

Hammett-Taft sigma constants Electron density TT-Bond reactivity Electron polarizability Dielectric constant Dipole moments Ionization potential Electron affinity... 

Charge transfer (ct) ionization potential, electron affinity... 

If we use B3LYP/VTZ+1 harmonics scaled by 0.985 for the Ezpv rather than the actual anharmonic values, mean absolute error at the W1 level deteriorates from 0.37 to 0.40 kcal/mol, which most users would regard as insignificant. At the W2 level, however, we see a somewhat more noticeable degradation from 0.23 to 0.30 kcal/mol - if kJ/mol accuracy is required, literally every little bit counts . If one is primarily concerned with keeping the maximum absolute error down, rather than getting sub-kJ/mol accuracy for individual molecules, the use of B3LYP/VTZ+1 harmonic values of Ezpv scaled by 0.985 is an acceptable fallback solution . The same would appear to be true for thermochemical properties to which the Ezpv contribution is smaller than for the TAE (e.g. ionization potentials, electron affinities, proton affinities, and the like). 

In principle, the behaviour of any molecular species in forming donor-acceptor complexes depends on its ionization potential, electron affinity and polarizability. However, the donor (or acceptor) ability of a substance depends strongly on the requirements and properties of its partners. The same compound may act as a donor towards strong acceptor compounds or as an acceptor towards donor compounds. This is the case of the TT-amphoteric p-tricyanovinyl-AA/V-dimcthylaniline (41) which is a donor towards 2,4,7-trinitrofluorenone and an acceptor towards /V,/V-dirnclhy Ian Mine138. 

The results of the alkylbenzene series may also be readily explained in terms of ir complex adsorption. In this series, the molecular orbital symmetry of individual members remains constant while the ionization potential, electron affinity, and steric factors vary. Increased methyl substitution lowers the ionization potential and consequently favors IT complex adsorption. However, this is opposed by the accompanying increase in steric hindrance as a result of multiple methyl substitution, and decrease in electron affinity (36). From previous data (Tables II and III) it appears that steric hindrance and the decreased electron affinity supersede the advantageous effects of a decreased ionization potential. The results of Rader and Smith, when interpreted in terms of tt complex adsorption, show clearly the effects of steric hindrance, in that relative adsorption strength decreases with increasing size, number, and symmetry of substituents. 

To determine how much HF is needed, we consider systems where s is significantly greater than 1, but where GGA still works reasonably well. In Ref. [18], we examined the ionization potentials, electron affinities, and electronegativities of a variety of atoms, as well as the atomization energies of several... 

Hydrogen bonding (hb) Dipole-dipole (dd) Dipole-induced dipole (di) Induced dipole-induced dipole (ii) Charge transfer (ct) qym, ME, orbital type dipole moment dipole moment, polarizability Polarizability ionization potential, electron affinity... 

STRUTINSKY S SHELL-CORRECTION METHOD IN THE EXTENDED KOHN-SHAM SCHEME APPLICATION TO THE IONIZATION POTENTIAL, ELECTRON AFFINITY, ELECTRONEGATIVITY AND CHEMICAL HARDNESS OF ATOMS... 

In the next section we shall recall the definitions of the chemical concepts relevant to this paper in the framework of DFT. In Section 3 we briefly review Strutinsky s averaging procedure and its formulation in the extended Kohn-Sham (EKS) scheme. The following section is devoted to the presentation and discussion of our results for the residual, shell-structure part of the ionization potential, electron affinity, electronegativity, and chemical hardness for the series of atoms from B to Ca. The last section will present some conclusions. 

Table 1 References to Semi-empirical Calculations of Ionization Potentials, Electron Affinities and...

The ability of molecules to form donor-acceptor complexes depends not only on their ionization potential, electron affinity and polarizability, but also on the requirements and properties of partners. 

Table 3. Experimental ionization potentials, electron affinities and absolute electronegativities of alkyl and fluorinated alkyl radicals [50-55]...

Commonly used descriptor variables for QSARs involving redox reactions include substituent constants (o), ionization potential, electron affinity, energy of the highest occupied molecular orbital (EHOMO)or lowest unoccupied molecular orbital (ELUMO), one-electron reduction or oxidation potential (E1), and half-wave potential (E1/2)- One descriptor variable (D), fit to a log-linear model, is usually sufficient to describe a redox property of P. Such a QSAR will have the form... 

Failures Heats of formation, ionization potentials, electron affinities, spectral transitions... 

---